Anger continues to rise in Kabul, a day after a huge bomb hidden in an ambulance killed nearly 100 people and wounded several others, highlighting the ability of insurgents to strike at the heart of Afghanistan.

At least 95 people were killed and 191 wounded in the lunchtime attack claimed by the Taliban, which caused panic in the war-torn capital and overwhelmed its hospitals.

US President Donald Trump called for "decisive action" against the Taliban over the assault, the second it has carried out in the war-torn city in a week, as other international leaders also condemned the attack.

Ordinary Afghans took to social media to express their anguish and sorrow at the rapidly worsening security, as the Taliban and Islamic State group step up attacks on Kabul, turning it into one of the deadliest places in Afghanistan for civilians.

"We are so heartbroken in Kabul that we don’t know how to start our new day," Freshta Karim wrote on Twitter.

"Shall we stay home or go to work, shall we meet our friends and cry or shall we force ourselves to create an illusion of hope? How are you starting your day in Kabul?"

The blast happened in a crowded area of the city where several high-profile organisations including the European Union have offices.

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The force of the explosion shook windows of buildings hundreds of metres away and caused some low-rise structures in the immediate vicinity to collapse.

The government has blamed the Taliban-affiliated Haqqani Network, which Afghan and Western officials suspect of involvement in at least some of the recent attacks in the capital.

The suicide bomber passed through at least one checkpoint in the ambulance, saying he was taking a patient to Jamuriate hospital, an interior ministry spokesman told AFP on Saturday.

"At the second checkpoint he was recognised and blew (up) his explosive-laden car," Nasrat Rahimi said.

Rahimi told a news conference later that most of the victims were civilians. Four suspects have been arrested.

The attack came exactly a week after Taliban insurgents stormed Kabul's landmark Intercontinental hotel and killed at least 25 people, the majority foreigners.